Heat sealing of Teflon electrets by annealing

The delayed radiation-induced conductivity (DRIC) generated in the irradiated volume of Teflon FEP electrets charged by electron-beam injection can be eliminated by annealing at temperatures between 100 and 180 °C for periods of the order of 10–106 sec. The decay and eventual disappearance of the DRIC may be studied by themally stimulated current (TSC) measurements. While the irradiated region of the material shows a short-circuit TSC peak at temperatures between 40 and 100 °C, depending on time after charging, the peak temperature of the annealed Teflon is at 180–190 °C corresponding approximately to the characteristics of the nonirradiated material. The electrets are thus ’’heat sealed’’ in the sense that conduction in the irradiated region is reduced to the values observed for nonirradiated Teflon. Teflon films charged by other methods exhibit more severe electrical changes which cannot be completely eliminated with the present method.